When a carpet snake senses motion or vibrations caused by any creature walking on its carpet, it begins to take shape in 2-4 rounds.
If we go with a camouflage ability (ie, Spot check required to notice), I'd definitely say so.Should someone with ranks in Craft (weaving or rugmaking) get a bonus on checks to recognize one of these creatures?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.